Apple’s Worldwide Developers Conference is only hours away. (The event starts at 1pm EST/10am PST.) But that hasn’t stopped the speculation machine from going full-bore. The latest rumor: TechCrunch has acquired a “leaked” image (above) of what may or may not be the new iOS 5 home screen. If genuine, the picture would confirm two of the most likely updates to Apple’s mobile operating system, namely a revamp of notifications and system-level Twitter integration.

Of course, it’s far more likely that the pic is just a skilled Photoshop job from some undergraduate design student. But who knows? At this point, anything’s possible.

The image shows a grey bar near the top of the home screen with the Twitter bird logo and “2 Mentions” written on it. Since none of this is possible with iOS 4, it would mean that Apple has updated the iOS notification system in a similar way to how it displays the personal hotspot feature, or an ongoing phone call. It would also mean that Twitter will have a much deeper integration with iOS than it had before.

Whether or not this photo actually shows the new notification system or not, it’s probable that we’ll see something similar during today’s announcement. In addition to new notifications and Twitter (and possibly Facebook) integration, rumors indicate that iOS 5 will also include a widgets feature that would be reminiscent of Mac OS X’s Dashboard.

On top of all that, the big news out of WWDC will likely be the new iCloud feature, which could usher in a new era for Apple that enables its highly popular touchscreen devices — iPhone, iPad and iPod touch — to operate, update and stay connected without the need for a wired sync with a PC or Mac.

Regardless, we’ll all know what is and what isn’t included in iOS 5 in just a few hours. So stay tuned.

Update: According to Joshua Topolsky at This Is My Next, iOS 5 will have a new notification system that will be “located at the top of the screen,” but the image above and others like it “are not the real deal.” He adds that the new system will be similar to the MobileNotifier app for jailbroken iPhones, and messages “will appear and then slide back up in a unobtrusive manner, similar to webOS.” Topolsky also says that Apple will introduce a internal iPhone texting service, a la BlackBerry Messenger, that will enable iPhone users to chat with each other, and bypass carriers altogether.